U.S. Pat. No. 4,564,541 discloses a hollow plastic container having a laminated structure comprising a layer of poly(ethylene terephthalate) and a gas barrier layer of an olefin-vinyl alcohol copolymer wherein the layers are laminated by an adhesive layer composed of copolyester. Such containers will have a poor appearance because of lines or striations existing in the container due to the variation in thickness of the barrier layer or adhesive layer, or both, resulting from the forming process and the blowing process. In addition, in such containers, the peel strength decreases during elongation or blowing. The containers also do not have good thermal stability so that the containers can be filled with hot contents.
In copending application, Ser. No. 841,651, filed Mar. 20, 1986, now U.S. Pat. No. 4,713,269, having a common assignee with the present application, there is disclosed a heatset container made from a parison comprising at least one layer of poly(ethylene terephthalate) and a barrier layer of a copolyester without the use of an adhesive. The resultant container has properties comparable to heatset poly(ethylene terephthalate). The interlayer adhesion between the poly(ethylene terephthalate) and the copolyester were found to be essentially the same as a non-heatset multilayer container of the same layers.
Among the objectives of the present invention are to provide multilayer containers which have high barrier properties; improved thermal stability, that is capable of being hot filled at elevated temperatures; have good interlayer adhesion; have layer uniformity; have good transparency; and be light in weight.
In accordance with the invention, a multilayer biaxially oriented heatset article and method of making forming a preform comprising an outer layer, an inner layer of poly(ethylene terephthalate), an intermediate layer of olefin-vinyl alcohol copolymer, a layer of adhesive laminating the olefin-vinyl alcohol copolymer layer and the outer layer and a layer of adhesive laminating the olefin-vinyl alcohol copolymer layer and the inner layer. The preform is then heated to orientation temperature and blown against a heatset hot mold to produce an article such as a container that has high barrier properties, improved thermal stability, i.e., capable of being hot filled at elevated temperatures, have layer uniformity, good interlayer adhesion, good transparency and is light in weight.